Language packs and upgrading to 1.3.7?

We currently have a 1.2.5-based store in English and want to provide translated versions of it in French and Japanese to start, and additional languages in the future.

It appears that there are updated language packs for 1.3.7 for both French and Japanese. But it's unclear if there are language packs for 1.2.5 for those languages or that can otherwise be easily updated. Maybe someone could shed some light on the subject?

Any other thoughts on the benefits of upgrading to 1.3.7 in this scenario would be welcomed.

Thanks!

I suggest that you upgrade and then apply the lang packs -

Actually set up a new install in a folder and work out the issues first

Absolutely agree with Kobra. There have been a lot of security updates since 1.2.5. It's worthwhile bring yourself up-to-date and then the language packs should go in very easily.